An enormous explosion erupted from behind the sun on Monday, and scientists think its source could be rotating toward the Earth in the coming days. On September 5, NASA's STEREO-A spacecraft recorded a significant coronal mass ejection (CME)—an eruption of plasma and magnetic activity from the sun's atmosphere—that occurred on the far side of the sun. Since the CME did not occur in the direction of Earth, scientists spotted it by its "halo," a giant shockwave that could be seen from Earth's position on the other side of the sun. The halo of the huge coronal mass ejection on September...